I recently came across a repository of jewels in the form of the unpublished manuscripts of E.W. Dijkstra. I just finished reading one entitled "Some Meditations on Advanced Programming". It is amazingly well written and still so relevant to present-day computer science, that I recommend anyone with at least a passing interest on the subject to read it.
I was pleasantly surprised to find in the last remark of the manuscript, something which can be considered, IMHO, the most fundamental design principle of Python and the my main reason to love it. I quote:
"As my very last remark I should like to stress that the tool as a whole should have still another quality. It is a much more subtle one; whether we appreciate it or not depends much more on our personal taste and education and I shall not even try to defined it. The tool should be charming, it should be elegant, it should be worthy of our love. This is no joke, I am terribly serious about this. In this respect the programmer does not differ from any other craftsman: unless he loves his tools it is highly improbable that he will create something of superior quality.
At the same time these considerations tell us the greatest virtues a program can show: Elegance and Beauty."